Material palette and drag-and-drop fixes

This update enhances the material palette and resolves issues related to Toon material exports and disappearing layers during drag-and-drop actions in the asset editor.

Changes

• Visual improvements on the material palette.
• Fixed issue with Toon material in exports.
• Fixed disappearing layers during drag and drop in asset editor.
• Fixed z-fighting issues in frame mode and image exports.
• Minor bug fixes.